Chicken coup A giant, 200-kilogram "chicken from hell" that resembles an Australian cassowary roamed Dakota at the same time as T. rex, US scientists reveal today.

And while the "weird-looking" bird may have eaten the odd mammal, it would have been chips for this chicken if it had crossed T. Rex's path.

The revelation comes as another team of researchers has unveiled 126-million-year-old fossils, found in China, of the oldest-known stick or leaf insect.

The chicken-like dinosaur, Anzu wyliei , had a head shaped like a bird's, a toothless beak, hands with big sharp claws, long legs for fast running and was probably covered in feathers.

A bizarre crest on its head is similar to that found on the cassowary, a flightless bird native to Australia and New Guinea.

Anzu wyliei measured about 3.5 metres long, 1.5 metres at the hip and weighed about 200-300 kilograms, the researchers say.

"It has the nickname 'the chicken from hell'. And that's a pretty good description," says palaeontologist Dr Matt Lamanna of the Carnegie Museum of Natural History in Pittsburgh, who led the research published in the journal PLOS One.

"If you could get in a time machine and go back to western North America at the end of the age of dinosaurs and see this thing, I would say your first reaction might be, 'What a weird-looking bird'," Lamanna says. "It would not look like most people's conception of a dinosaur."

On the menu

It is the largest North American example of a type of bird-like dinosaur well known from Asia. Its extensive remains offer a detailed picture of the North American branch of these dinosaurs that has remained mysterious since their first bones were found about a century ago, the scientists say.

Fossils of feathers are extremely rare and they were not found with any of the three partial skeletons of Anzu wyliei. But the researchers believe it had feathers based on fossils of close relatives from China that have clear evidence of them.

A. wyliei lived at the sunset of the age of dinosaurs, not long before an enormous meteorite is thought to have struck Earth about 65.5 million years ago and wiped them out along with hordes of other creatures, while sparing many birds.

It lived in a humid, low-lying environment dotted with rivers and swamps and lush with vegetation and plant-eating dinosaurs like the horned Triceratops, armoured Ankylosaurus, dome-headed Pachycephalosaurus and duck-billed Edmontosaurus.

But also hanging around the neighbourhood was one of the fiercest predators in Earth's history, Tyrannosaurus rex.

A. wyliei may have been an omnivore, munching on leaves, fruits or flowers while also swallowing the occasional mammal foolish enough to cross its path, the researchers say.

But it probably needed to be careful not to end up on someone else's menu.

"To a T. Rex, this thing would not look like a 'chicken from hell'. It would look like lunch," Lamanna says.

Ancient camouflage

Also in PLOS One today an international team of scientists has released details of its discovery in China of the fossil of an insect that lived about 126 million years ago whose appearance mimicked that of a nearby plant.

It is the oldest-known stick or leaf insect that used such natural trickery, the team says.

The insect, named Cretophasmomima melanogramma, was found in Liaoning province in northeastern China, part of the Jehol rock formation that has yielded many stunningly detailed fossils of creatures like early birds and feathered dinosaurs.

The researchers realised the insect looked remarkably like the leaf of a plant that grew in the same place at the time that was a relative of the Ginkgo tree.

The fossil shows wings with parallel dark lines that, when the bug was in the resting position, seem to produce a tongue-like shape that could hide its abdomen, they say. The plant had similar tongue-shaped leaves marked with multiple lines.

The researchers think the insect evolved to look like these leaves - even their green colour - and concealed itself from predators by mingling with the foliage. Females of this insect were estimated at about 55 millimetres long and the males a bit smaller.

There are roughly 3,200 known species of stick and leaf insects, which are members of the insect order known as Phasmatodea, derived from the ancient Greek word for phantom for their ability to seemingly disappear into the background.

Cretophasmomima melanogramma lived during the Cretaceous, the last of the three time periods that make up the Mesozoic Era, sometimes called the Age of Dinosaurs.

The arrival of small insect-eating birds and agile, branch-walking mammals provided good reason for insects to develop new predator-avoidance strategies like mimicking the appearance of a leaf, Bethoux says.

The researchers say this insect lacked some characteristics of similar insects seen today, such as a curved part of the front legs that hide the head.